1. Field of the Invention
The present invention relates to a vehicular power supply device mounted on a vehicle equipped with an idle stop function of automatically stopping/starting the engine (internal combustion engine) serving as a drive source of the vehicle.
2. Description of the Related Art
In order to decrease burdens on the environment, vehicles equipped with an idle stop function (automatic stop/start system) have been increasing in number in recent years, aiming at enhancing gas mileage. Those vehicles equipped with the idle stop function frequently repeat an automatic stop/start in running in urban areas and the like; therefore, it has now turned out to be technical issues how to reduce racing of the engine revolution speed and noise, secure startability of the engine and suppress a voltage drop at the lead battery at the automatic start.
In Patent Document 1, in a vehicle equipped with the idle stop function and with both a generator and a starter, its generation voltage is kept raised in automatically starting, whereby the racing of the engine revolution speed is prevented from occurring at the automatic start.
In Patent Document 2, electric power generated by the generator is stored in a battery, whereby power generation is stopped while the battery is being discharged, and energy consumption in the drive source such as the internal combustion engine can be reduced, thereby stabilizing generation output from the generator as well as securing engine startability by the operation of a starting means.    Patent Document 1: Japanese Laid-Open Patent Publication No. 2010-53794    Patent Document 2: Japanese Laid-Open Patent Publication No. 2010-104123
However, in the configuration shown in Patent Document 1, the lead battery voltage is lowered by discharging of the battery attributed to the operation of the starting means at the automatic start, and as a result, electrical equipment is reset, causing a problem of malfunctions occurring. Moreover in order to secure the engine startability, the generation voltage is likely to become zero, causing also another problem in that the power generation is unstable after the automatic start.
Moreover in the configuration of Patent Document 2, the engine startability by the operation of the starting means at the automatic start is secured by stopping the generator at the automatic start; however, the lead battery voltage is dropped by the discharging of the battery attributed to the operation of the starting means, causing another problem of malfunctions occurring with the electrical equipment reset.